GrovePi Kits for the Raspberry Pi

If you are looking to interface sensors to the Raspberry Pi (RBPi), the popular single board computer, GrovePi+ from Dexter Industries (SEED Studios) makes it very easy with their starter kit. The kit carries a GrovePi+ board, including more than 10 carefully selected sensors along with the necessary interfacing cables. The kit is very easy to use, as the user only has to plug the GrovePi+ board over your RBPi, and connect the necessary sensor to the board. GrovePi provides a powerful platform for any user to start playing with sensors and hardware.

The simplicity of the GrovePi+ board is evident, as you do not need any other hardware connection—only plug in the board atop the RBPi and initiate communications between the two boards over an I2C interface. The GrovePi+ board acts like a shield and the user can connect any of the Grove sensors from the kit to the universal Grove connector on the board, using the universal 4-pin connector cable available with the kit.

The GrovePi+ board has an ATMEGA328 micro-controller on it, and the Grove sensors, both analog and digital, connect to it directly. The RBPi also communicates with this micro-controller, which performs as an interpreter for the Grove sensors, sending, receiving, and executing commands the RBPi sends it. You can use any RBPi model with the GrovePi+, selecting from among RBPi A+, B, B+2, or B+3

GrovePi+ forms the hardware system for connecting, programming, and controlling sensors that help build your own smart devices. GrovePi+ is small—the size of a credit card—however, it is very powerful. You can think of the GrovePi+ kit as an Internet of Things kit for the RBPi—allowing you to connect numerous sensors to the RBPi—simply by connecting a cable from the GrovePi+ board to the sensor. The manufacturer’s website offers several software examples you can download and try. Alternately, you can write your own programs for the RBPi to control and automate any device.

GrovePi+ does away with the need for connecting sensors to the IoT using breadboards and soldering the sensors. Now it is only necessary to plug in the sensors and start programming directly. Therefore, GrovePi+ is and easy-to-use modular arrangement for hacking your hardware with the help of the RBPi and the Internet of Things.

Using the GrovePi+ system, one can connect over 100 types of sensors to the RBPi. The collection of sensors offered are all inexpensive and plug-n-play modules to sense and control inputs from the physical world. This provides countless possibilities of interacting with sensors, integrating them with the module and the RBPi to obtain unparalleled performance with ease.

For instance, Lime Microsystems and the SEED Studio have a new kit providing everything to start up a Software Defined Radio (SDR) with the RBPi and develop IoT applications for it. The LimeSDR Mini kit targets educational use and is meant for beginners. Lime has optimized the building block for use at 433/868/915 MHz and provides the necessary antennas in the kit. The kit also has an array of sensors from Grove and boards related to output from SEED Studios. The GrovePi+ board offers the computing power for the SDR, and you can use an RBPi 2, 3, or Z.

Magnetic Sheets Prevent Noise from Spreading

Electrical or magnetic noise is a byproduct of electrical activity within an operating device, and it causes several types of nuisance. A device generating a strong electrical or magnetic interference (EMI) can influence a nearby device, making it malfunction or even prevent it from operating at all. The extent to which a device affects another with its electrical or magnetic fields is called its Electromagnetic Compatibility, while the extent to which a device is susceptible to external electrical or magnetic fields is called its Electromagnetic Susceptibility.

Engineers make efficient use of such electromagnetic characteristics of devices. For instance, smartphones and other devices have wireless charging technology and near-field communication. Both make use of electromagnetic fields, the first to charge the device, and the other, allowing communication with nearby devices, both without any physical connection.

The above requires effective shielding and suppression of noise from electronic products. Magnetic sheets offer one such method, with the TDK Corporation offering the latest types of noise suppressing sheets, the IFM10M, a new addition to its Flexield series. TDK claims its new magnetic sheet suppresses noise over a frequency range of 500 KHz to 10 GHz. This is useful for several types of electronic devices, such as industrial terminals, point-of-sale systems, stylus pens, notebooks, tablets, and smartphones.

Featuring a laminated design, the IFM10M series of magnetic sheets consist of a copper-plated layer and a magnetic layer sandwiched together. Although there are several other types of magnetic sheets available in the market, the IFM10M sheets are exceptional as they are only 0.04 mm thick, making them over 60% thinner than their existing counterparts, but offering the same performance. IFM10M sheets are available in sizes of 300×200 mm, with an operating temperature range of -40 to +85°C.

As the IFM10M sheets are so thin, they are well suited for slim products such as stylus pens, notebooks, tablets, and smartphones. Their thin and flexible nature allows installation in dense environments. As the design of electronic devices is making them ever thinner, electronic components are also being mounted in higher densities. The increasing density of packing electronic components together leads to increase in noise emissions from components and cables causing more interference within the device.

By using IFM10M magnetic sheets on power coils, SOCs, and attaching them to the surface of flexible boards and cables, it is possible to reduce the effects of noise emission from one printed board to another.

The new magnetic sheets can improve both electromagnetic compatibility and electromagnetic susceptibility. The noise-absorbing properties of IFM10M reduce the effect of radiated noise as applicable to radiating sources. At the same time, the sheets can also protect components and circuits that are vulnerable to emissions of external noise and thereby reduce their potential impact.

Users can cut the IFM10M magnetic sheets to desired size to fit within available space. They can even shape them as required and install them in very small gaps, as the sheets are very thin and flexible. According to TDK Corporation, the magnetic sheets can improve the sensitivity of receivers for devices using stylus as inputs as these utilize inductive coupling.

High Accuracy Digital Temperature Sensor

Analog Devices is offering a high accuracy digital temperature sensor that covers a wide industrial range. The tiny package also incorporates a humidity sensor. There is no necessity of adding a separate analog to digital converter to this sensor, as the device has one built into it, and provides a high-resolution digital output of 16 bits. With a wide operating voltage range, the device is suitable for industrial, domestic, and commercial use.

The ADT7420UCPZ-R2 from Analog Devices measures temperatures from -40°C to +150°C, while operating from a voltage range of 2.7 to 5.5 V. The device is available in a 4 mm x 4 mm package commonly known as Lead Frame Chip Scale Package (LFCSP). This wire bond plastic encapsulated near chip scale package has a substrate of copper lead frame within a leadless package format. Input/output copper pads are positioned on the perimeter edges of the package.

This allows the user to solder the perimeter pads and the exposed paddle available on the bottom surface of the package to the PCB. The exposed thermal pad on the bottom of the package conducts heat away from the package when it is soldered to the copper layer on the PCB. The thermal and perimeter pads are tin plated to provide good soldering.

Within the ADT7420 is an internal band gap reference, along with a temperature sensor. The 16-bit ADC within the device monitors the temperature and digitizes it to a resolution of 0.0078°C. By default, the ADC resolution is set to 13 bits or 0.0625°C, which should be adequate for most users. However, the user can change the ADC resolution via a programmable mode, to 16 bits. The programmable mode is accessible to the user through an I2C serial interface.

Analog Devices guarantees the ADT7420 will operate reliably when supplied from 2.7 V to 5.5 V. Typical current consumption by the device id 210 µA when operating from a supply voltage of 3.3 V. The user can optionally power down the device to make it enter a shutdown mode where the current consumption is typically 2.0 µA at 3.3 V. There is an additional power saving mode, where the user programs the device to read one sample per second. The temperature drift for ADT7420 is merely 0.0073°C.

The ADT7420 exhibits very high temperature accuracy of ±0.20°C between -10°C and +85°C, when working from a 3.0 V supply. When working from a wider supply voltage of 2.7 to 3.3V, the temperature accuracy of the device is ±0.25°C between -20°C and +105°C. As soon as the device powers up, the first temperature reading is available within 6 ms.

Implementing the ADT7420 is very easy, as it does not need any temperature calibration or correction by the user. The user also does not require any linearity correction for the usable temperature range. The user can program the device to produce an interrupt when it senses the temperature crossing a preset critical temperature.

Applications for the ADT7420 include replacement for RTD and thermistor, and compensation for thermocouple cold junction. Typically, the device is usable in medical equipment, and for industrial control and test, food transport and storage, environmental monitoring and HVAC, and Laser diode temperature control applications.

Tree-Axis High Resolution Digital Accelerometer

Most modern smartphones can sense whether their users are holding them in the portrait or in the landscape position, accordingly adjusting the displayed image. Additionally, while playing games such as Temple Run, the smartphone can respond to tilting by changing certain functions in the game. The smartphone accomplishes this motion sensing as it has an accelerometer IC working inside it.

Apart from smartphones, several other applications make use of accelerometers. For instance, car alarms can be programmed to alert their drivers as soon as they cross a certain speed threshold. Hill Start Aid (HSA) systems depend on accelerometers to alert drivers when their vehicles start climbing a defined slope. Accelerometers tell weighing machines whether a vehicle is properly positioned before starting to take readings. Black boxes or data recorders in airplanes, trains, and other vehicles stop recording when an accelerometer decides there has been a violent incident.

Analog Devices makes ADXL313, one of such versatile digital accelerometers. The device has very high resolution of 13 bits on each of its three axes, and is capable of measuring up to ±4 g, where 1 g is the normal level of acceleration due to gravity at sea level. ASXL313 offers a 16-bit data output in a two’s complement format. The user can access this digital output through either an I2C serial interface, or a 3- or 4-wire serial port interface (SPI).

Being very small, only 5x5x1.45 mm, ADXL313 comes in a lead-free, RoHS compliant, LFCSP package and is qualified for automotive applications with a wide operating temperature range of -40°C to +105°C. The device is capable of surviving shocks up to 10,000 g. ADXL313 can work with a wide supply range of 2.0 to 3.6 V, consuming ultra-low levels of power. At a supply voltage of 3.3 V, the ADXL313 consumes only 30 µA in measurement mode, and only 0.1 µA in its standby mode.

While its embedded FIFO technology minimizes processor load for the host, ADXL313 offers an exemplary noise performance of typically 150 µg/√Hz for its X- and Y-axes, and typically 250 µg/√Hz for its Z-axis. While its user-selectable resolution is limited to a 10-bit resolution for any g value on the low side, its sensitivity is a minimum of 1024 LSB/g for any g range. On the upper side, its resolution scales from 10-bits at ±0.5 g to 13-bits at ±4 g. ADXL313 features a built-in motion detection function for monitoring activity/inactivity.

The ADXL313 3-axis digital accelerometer offers its user several flexible interrupt modes, which the user can map to two interrupt pins. Along with the built-in sensing function, the device can sense the presence or absence of motion, and detect whether the acceleration on any axis is exceeding the user-set level. The user can map these functions on two interrupt output pins, which can alert the controlling micro-controller accordingly.

ADXL313 has an integrated 32-level FIFO register to store data. This minimizes host processor intervention leading to a huge reduction is system power consumption. This low power mode enables intelligent motion-based power management and empowers the device with threshold sensing and active measurements while dissipating extremely low levels of power.

Using Reed Switches as Sensors

Any ordinary electrical switch has two contacts. Push-type switches are spring loaded so that pushing a button brings them together and they spring apart on releasing the button. Rocker switches have mechanical levers that close the contacts when in one position, while in the other position they pull apart.

In reed switches, the two contacts are in the shape of metal reeds, each coated with a metal that does not wear easily. The reeds are made from a ferromagnetic material, so they are easy to magnetize. The entire assembly is hermetically sealed within a thin glass envelope containing a nonreactive gas such as nitrogen. For extra protection, sometimes the glass envelope may have a plastic casing.

The ferromagnetic material making up the reeds is typically a nickel-iron alloy that shows high magnetic permeability but low magnetic retentivity. That means, when brought close to a magnet, it magnetizes the reeds, which come together in contact. On moving the switch away from the magnetic field, the reeds lose their magnetic property and separate. Their movement has high hysteresis, that is to say they close and open slowly and smoothly. The reeds have a flat area where they contact each other, and this helps to extend the life and reliability of the switch.

Although reed switches typically have two ferromagnetic contacts, some variants may have only one ferromagnetic contact, while the other is non-magnetic. Others may have three contacts, with two non-magnetic and the central one as ferromagnetic.

Like ordinary switches, reed switches also come as two major variants—normally open type and normally closed type. This refers to the position of the reeds when there is no magnetic influence on them. Therefore, the normally open type has its reeds separated from each other, and they close when a magnet is brought close enough. The normally closed type of reed switch has its reeds in contact with each other, and they move apart when a magnet is brought close enough.

As the magnet comes close to a normally open reed switch, the two contacts become magnetized as opposite magnetic poles, and they attract each other to close. In this position, the switch can pass an electric current. This magnetizing of the reeds is independent of the pole of the magnet coming close to them. As the magnet moves away, the reeds lose their magnetism, and their stiff and springy nature makes them spring apart in their original position.

Reed switches are very useful as sensors such as for sensing level of liquids. A sealed stem holds the reed switches at different heights. A float containing a permanent magnet rides on the stem, going up and down as the liquid level changes. When the float magnet comes close to one of the reed switches, it snaps close, changing its electrical status that any electronic circuit can sense. Automotive, marine, and industrial applications use reed switches for level sensing.

A float switch in a dishwasher controls the level of water in the machine. The shaft containing the reed switch is positioned at the water fill limit of the pan. As the water rises, so does a float containing the magnet. When the magnet comes close to the reed switch, it closes, and signals the ECU.

How to Keep Your Bearings Running Cool

Electronic gadgets rely on a host of equipment for their creaseless performance. One of them is power generating equipment—spinning generators, motors, and shafts that create and transmit power. In fact rotating machinery is the basis not only of electronic gadgets, but also of modern civilization itself. A wide variety of lubricated and self-lubricating bearings keeps these machines operating smoothly and efficiently. Heat is a major factor affecting bearings, degrading its lubrication and damaging the bearing, ultimately increasing friction and decreasing efficiency.

Normal operations rarely merit concerns over temperature rise of bearings. However, exposure to abnormally high loads and speeds, high ambient temperatures, and hot process fluids can cause problems.

For instance, roller bearings can start to run hot because rolling elements microslip on the races. Another reason is the contact stress generated hysteresis of rolling elements and race materials. Even the sliding between the pilot surfaces or rolling elements and their separator and the sliding between guide flanges and rollers generates heat. Shear and turbulence in the lubricant also generates some heat.

One of the best means of heat control in bearings is by using cooled oil, particularly useful in gas turbines and pumps for hot liquids. Although lubrication needs only a thin film of oil, high flow rates of oil can also help to cool bearings. The common practice is to set the nominal oil level to the center of the bottom ball bearing. This works satisfactorily except for extremely high speeds, when an oil flinger providing a mist of oil becomes necessary. In places where the above cannot be used, heat is removed by convection from the bearing housing to the ambient air.

Thrust bearings are susceptible to the viscosity of the lubricant they use. Viscous friction can cause power loss, which can be substantially reduced by lower lubricant viscosity. However, the best way of keeping thrust bearings cool is increase the volume of oil flowing over each pad segment. Another method often followed by engineers is to directly cool the oil feed or cool the bearing housing from the outside. Using copper plates in place of steel backing also helps to keep bearings cool, as copper conducts heat away better than steel does.

Sleeve or journal bearings have a longer life when running cool. Therefore, it is important to take steps to bring down the operating temperature. Although sleeve bearings also benefit from lower viscosity oil, the cooling effects are somewhat limited. This is because the viscosity of the oil film rises as the overall temperature drops. Nevertheless, low viscous oil helps in cooling sleeve bearings in high-speed machinery.

Engineers strive to maintain an optimal radial bearing clearance as this has a pronounced influence on bearing performance and hence its operating temperature. If normal clearance is small, the sleeve bearing can run hot and the cooler housing can constrain it, leading to a seizure.

Too much clearance can also lead to vibration, unbalance, and other instabilities. To avoid such undue vibration and temperature rise, engineers must follow recommended diametrical clearances.

Industrializing your Raspberry Pi

You can turn your Raspberry Pi (RBPi) into a completed computer system with the minimal effort. Using a pre-assembled, cost-effective kit will not only save you a lot of time, but also speed up the installation and slash development time as well, allowing you to realize the full potential of your single board computer. This industrialization of your SBC brings huge commercial potential and encompasses a wide range of applications, including using the system for payment terminals, communication systems, IoT products, home technology, medical devices, machine tool control systems, industrial automation, and more.

The PCAP 10.1-inch Touch Screen Kit from Inelco Hunter is specially designed to work with the popular single board computer, the RBPi. You can buy the kit in pre-assembled form and simply mount the RBPi onto the interface PCB on its rear, fixing it in place using the supplied pillars and screws. You can then mount the display as a panel or flush mount it to get resolutions up to WXGA.

Customers looking for a larger screen format for the RBPi can now upgrade from the earlier 7-inch display format from the same designer, Anelco Hunter. He developed this new screen for customers looking for extra screen space. Using the kit, customers can industrialize their equipment quickly and easily by providing it with a larger screen. No further upgradation is necessary, as the same programs and software already available for the 7-ich version will continue to be useful.

According to the Managing Director of Inelco Hunter, David Bushnell, the idea for a bigger screen format for the RBPi was born after a number of customer requests were made following the launch of their 7-inch kit. The kit maintains the same quality of the 7-inch model’s TFT screen with industrial grade while transitioning to the bigger screen format, maintaining the earlier high-quality metrics and ongoing availability.

A PCB provides the connections on-board for HDMI interface, along with the required conversions for signal, power, and backlight required by the TFT display. To drive the TFT display, the user has to supply it with 12 V at 2 A. This is apart from the 5 V at 2 A the RBPi requires for operating.

The PCAP touchscreen offers features such as pinch, zoom, and rotate through either USB or I2C connection. While the screen dimensions are 255 x 174 x 9 mm, the view area is 218 x 137 mm. The wide-angle IPS display offers a resolution of 1280 x 800 pixels.

Inelco Hunter has designed their display kit to work with all models of the RBPi family. They have tested the kit to operate at temperatures of +70°C and this underlines its reliability. This further supports the mean time before failure (MTBF) figure of 50,000+ hours. All these specifications make this display a good choice for those looking for a design with a long life and reliability.

Customers buying the kit will find a 10.1-inch Touch Screen TFT display, a pre-assembled interface PCB for HDMI to LVDS conversion, a connector for HDMI to HDMI interface, a micro USB to USB cable interface, and the pillars and screws for mounting the RBPi.

What are Digital Pressure Sensors?

Various industrial systems use pressurized air, water, and other fluids. They use sensors to regulate and maintain proper pressure at different points in their activities. Although many systems continue using analog pressure sensors, digital versions are fast replacing them. A few examples serve to illustrate why pressure sensors are important.

Industrial icemakers need water at minimum pressure between 20 and 40 psi at the inlet—this allows the water inlet valve to function properly—although the exact water pressure requirement is dependent on the particular make and model of the refrigerator.  Pressure sensors with media isolation (waterproofing) provide a quick method of determining whether the water pressure is adequate for making ice.

Corporate Average Fuel Economy (CAFE) regulations demand that by 2025, the average fuel economy should be 54.5 MPG fleet-wide. Although popular belief is, each car maker’s fleet should have a significant presence of electric and hybrid vehicles to meet CAFE requirements, manufacturers are working towards advanced diesel and gasoline engines that should be able to meet the standards by themselves. One model of such advanced engines is the Achates Power Opposed-Piston engine. It exhibits fuel economy gains of 30-50% with significant reduction of emission, and is more cost effective compared to other solutions. The Achates engine requires a fuel injection system capable of a 2000 bar injection pressure.

For cutting different types of very hard, heat-sensitive, or delicate materials, industrial machines often make use of a water-jet cutting system. This avoids heat damages to the workplace edges or surface. An ultra-high-pressure pump operating at 40,000-100,000 psi produces a high velocity, high-pressure stream of water at 30,000-90,000 psi. Special MEMS pressure sensors are necessary to achieve the desired accuracy, resolution, and repeatability in such high-pressure measurement systems.

All Sensors makes the DLVR Series of mini digital output pressure sensors based on their patented CoBeam2 TM Technology, providing overall long-term stability by reducing susceptibility to package stress. Compared to single die systems, the DVLR differential pressure sensor technology improves the position sensitivity.

The DC supply voltage option of 3.3 or 5 V eases the integration of the sensors into a wide range of measurement and process control systems. I2C or SPI interface options allow direct connection to serial communication channels. The sensor goes into very low-power modes between readings, thereby minimizing load to power supply for battery operated systems.

With a pressure range of 0.5 to 60 inH2O and a common mode pressure of 10 psig, the DLVR pressure sensors offer better than 0.5% accuracy over temperature. While the storage temperatures range from -40 to +125°C, the sensors can operate from -25 to +85°C, under non-condensing humidity limits between 0 and 95%. The sensors are available in ten types of device packages including E1NS, E1ND, E1NJ, E1BS, E1BD, E2NS, E2ND, E2NJ, E2BS, and E2BD.

The DLVR series of digital output sensors are compensated and calibrated by the manufacturer and provide a stable and accurate output over a wide range of temperature. Intended use for this series involves non-ionic and non-corrosive working fluids such as dry gases, air, and similar. Moisture or harsh media protection is also available in the form of an optional parylene protective coating.

Interfacing XBee Modules with the Raspberry Pi

You can use two XBee modules to exchange data between them, as they are modular, self-contained, and low-cost components using radio frequency to communicate. Most XBee modules transmit on the ling-range 900 MHz or on 2.4 GHz using their own network protocol.

The primary advantage of using XBee modules is their size—nearly as large as a postage stamp. Therefore, it becomes easy to use them as sensor nodes in small projects. They consume very low power, and incorporate a special sleep mode that reduces their power consumption considerably. This is of advantage when using them on battery or solar power.

XBee modules can read their data pins and transmit the collected data to another XBee module. Therefore, if you have a sensor node and a data-aggregator node, you can easily link them together with XBee modules. As there is no micro-controller on the XBee module, it has only a limited amount of processing power for controlling the module.

This limited processing power makes it suitable for several sensor nodes, but not for all. For instance, although the XBee module can read data from sensors, it cannot do so from sensors requiring algorithms to interpret or extrapolate meaningful data—the additional calculations this requires may need assistance from a microcontroller. Incidentally, configuring an XBee module with the Digi configuration tool, X-CTU, requires a computer running the Windows operating system. For other operating systems, use a virtual machine to run Windows.

The XBee line of wireless modules has a list of different types, and you must select the one most suitable for your project. Some modules support proprietary protocols from Digi, others support UART or SPI to 802.11 b/g/n (Wi-Fi), while others support the ZigBee, and 802.15.4 protocols.

Several popular XBee modules support the ZigBee protocol. Therefore, many projects use the ZigBee modules available in the market. ZigBee modules have several more choices based on application. For instance, there are ZigBee embedded surface mount modules, and others that support the ZigBee feature set, and 802.15.4 protocols. The most popular among these are modules supporting the ZigBee Pro feature set.

The advantage with ZigBee is it is an open standard based on the IEEE802 standard, useful for network communications. ZigBee supports the formation of mesh networks to configure and heal broken links automatically, and allows the use of intermediate probes to transmit data over long ranges.

You can use a ZigBee development module with on-board USB interface or use an FTDI cable to interface it. Usually, in a mesh topology, you will need to assign each node with their individual roles as coordinator, router, or end device. You will need at least one coordinator in the network, while the mesh will require several routers.

You can use the explorer dongle to plug in the ZigBee module, and use the USB connector on the dongle to plug the combination into one of the USB ports on the Raspberry Pi (RBPi). To communicate, you will need another pair of dongle and ZigBee module on the USB port of a computer or laptop. You will need to select the correct com port, and a common baud rate on a HyperTerminal to initiate communication between the modules.

What are Signal Generators?

While developing electronic systems, engineers test the device by stimulating it with different types of signals they expect it to encounter in the field. The piece of test equipment that engineers use for generating the various test signals is the signal generator. A signal generator may be used as a stand-alone development system or in combination with other test instruments.

Depending on the requirement, signal generators may come in various forms and types, with each of them providing different forms of signals. For instance, some output only RF signals, others audio signals, while some provide a train of pulses, and still others offer different shapes of wave-forms. Although different signal generators offer a variety of facilities and performance levels, they may be broadly classified as:

Function Generators

This type of signal generators typically generates simple repetitive waveforms such as sine, sawtooth, square, and triangular waveforms. Early models of signal generators used analog circuits to generate the waveforms, but later models depend on digital circuitry to produce them. Users can set the frequency for the waveforms from the front panel of the instrument. Function generators operating at high frequencies are more expensive.

Arbitrary Waveform Generators

These signal generators can produce arbitrary waveforms that the user specifies. They are one of the most complex function generators and therefore expensive. Users can demand almost any shape of waveform for the instrument to generate, sometimes even by specifying points on the waveform. Some manufacturers compromise on the bandwidth because of the techniques they use to generate the signals.

RF Signal Generators

As the name suggests, these signal generators output radio frequency signals. Earlier analog models used free running oscillators with frequency locked loop techniques for improved stability. Nowadays, manufacturers use frequency synthesizers for achieving the stability and accuracy. Some also use direct digital synthesis along with phase locked loops for generating the required RF output.

Vector Signal Generators

These are a special type of RF signal generators for generating complex modulation formats such as QAM, QPSK, and similar.

Audio Signal Generators

These produce signals within the human audio range, typically from 20 Hz to 20 kHz. Suitable for audio and frequency response measurements, some versions offer repetitive and non-repetitive linear and logarithmic sweeps across the entire output. Some audio signal generators can synchronize with an oscilloscope to enable a visual display of the frequency response of the device under test. Usually with very flat response and extremely low levels of harmonic distortion, audio signal generators help in the measurement of distortion from the device under test.

Pulse Generators

This type of signal generators output pulses with variable height, width, and rise/fall times. Users can program them to output a single pulse after a defined time delay. The user may program all aspects of the pulse—its height, width, DC level, and its rise and fall times.

The large variety of signal generators producing different types of waveforms allows engineers to use them in various applications. They are useful for testing RF equipment, logic boards, and in hosts of other areas. Of course, for achieving the proper objective, the engineer has to determine the type of signal generator necessary for a given job.